The invention is directed to a device for dividing an optical beam that is composed of at least one prism and comprises an entry face, a reflection face as well as two exit faces.
EP-A-0 354 028, corresponding to U.S. Pat. No. 5,011,245, discloses such a device. The device is employed therein in an inside drum recording means, whereby a recording material to be exposed is arranged in a stationary inside drum fashioned like a cylindrical segment. The sub-beams can be aligned with the rotating prism recited in this publication such that they have an offset of approximately 180.degree.. As a result thereof, two lines of the recording material can be exposed per revolution of the prism, as a result whereof the recording speed is increased. The device, however, has the disadvantage that the angular wobble of the rotating prism that is caused by tolerances in the region of the bearing unit for the prism is doubled and the recording quality is thereby substantially diminished.
Another device comprising a prism for deflecting a light beam is disclosed by DE-C-39 18 075. In this device, the angular wobble is in fact reduced but only one light beam is produced, so that respectively only one line on the recording material can be exposed during a revolution of the prism.
EP-B-0 126 469, corresponding to U.S. Pat. No. 4,595,957, discloses another inside drum recording means, whereby a light beam is deflected across the recording material with a single mirror. The employment of a single mirror has the disadvantage that the angular wobble is likewise doubled and only one line on the recording material can be exposed per mirror revolution.
WO 90/15355, corresponding to U.S. Pat. No. 4,936,643, discloses another device for-beam deflection in an inside drum recording means. In order to avoid the influences of disturbances, two reflection faces are arranged therein in the region of a rotating shaft. The first reflection face, which faces toward a light source, deflects the light beam in the direction onto the second reflection face, which aligns the light beam onto a recording material. This device has the disadvantage that only a single line can again be exposed on the recording material per revolution. The angular wobble is completely suppressed in this device.
U.S. Pat. No. 4,878,720 recites various prism shapes that completely suppress angular wobble and do not allow two sub-beams to be produced.
It is not possible with the assistance of the known devices to realize a beam splitter such that it is constructed in a structurally simple way and also guarantees a qualitatively high-grade beam transmission. In particular, the known devices are not in the position to adequately undertake a reduction of an angular wobble.